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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.


Hello Everyone. It is that time of year again. Time to approve changes to the competition rules for the new year.

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viewtopic.php?f=32&p=19486#p19486

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PVC Used for parts under pressure

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Should the use of PVC and CPVC be banned for pressurized components

Poll ended at Wed Oct 17, 2007 3:35 pm

Yes. Use should be only for non-pressurized applications (payload sections)
9
26%
No. Use at your own risk!
26
74%
 
Total votes: 35

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PVC Used for parts under pressure

Post by WRA2 » Mon Sep 17, 2007 3:35 pm

PVC and CPVC pipe is commonly used to make launchers and components of pressure vessels because it is cheap and readily available. PVC can shatter when it fails under pressure creating dangerous shrapnel. Should we ban its use in our competitions for components under pressure?


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Post by Drag_Racer408a » Mon Sep 17, 2007 7:30 pm

I think PVC should be allowed to be used for launchers ect. I know some people use steel and copper but for some the PVC is just easier and more reliable.

If the pvc is a saftey issue rather than an improper usage thing then the length between a presurized launcher or watever maybe should be increased.

I think some would get really mad about PVC beign banned because it is really cheap. As long as you stay within the saftey requirements of the rated pressure than it is really safe. I have only had a launcher 'blow up" once. But it wasn't really a pressre issue. It was a design flaw.

If PVC was indead banned then i personally would get pretty mad and probably drop the group. PVC is VERY safe if used properly. I know most of us around here are all pushing the limits to everything but the stuff is pretty safe.

Also your rocket would most likley blow up before your PVC launcher would because the sizes most used by our wrocket community can hold 600 PSI or more depending on the size.


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Post by tsumrall » Tue Sep 18, 2007 9:04 am

Define "components under pressure". My deployment device is under pressure. Does that count?

Also I read somewhere (since deleted) that the rules were not every going to change.

This is a good example of why your classes should be based on energy just like pyro-rocketry. If this was true then you could exclude PVC from high pressure systems but leave it in when it's safe to do so.


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Re: PVC Used for parts under pressure

Post by Spaceman Spiff » Tue Sep 18, 2007 1:37 pm

WRA2 wrote:PVC and CPVC pipe is commonly used to make launchers and components of pressure vessels because it is cheap and readily available. PVC can shatter when it fails under pressure creating dangerous shrapnel. Should we ban its use in our competitions for components under pressure?
I use PVC in my launchers and I think that it's no more dangerous than any other parts of the rocket. People can use metal parts like cameras and batteries and those can become projectiles in an explosion too. You already have the rules that require people stay 50 feet or more away and behind a shield and that should cover any PVC parts. It would be redundant and stupid to make us all change our designs at this stage of the contest. Don't do it.


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Post by The Mooseheads » Tue Sep 18, 2007 2:22 pm

Spaceman has the right idea. The rules already cover safety and rely on the competitors to adhere to the rules to insure safety. Metal pipes can shatter too if you exceed their design pressure, you rely on the individual to use only safe pressures for their design.

What needs to change is the wording of the rule so that you allow PVC and other parts as long as the rated pressure is not exceeded.

You could also say that failure to comply with a safety rule will get you banned from entering any contests for one full year or something.

That wouldn't be changing the rules, so nobody has to change anything. They should have been doing this all along.

FWIW, I don't know where I'd get a launch tube made from anything but PVC. I don't want to change the design. I voted to allow PVC! I realize the rule would be not be unfair because everyone is in the same boat as me, but I'd be annoyed to have to rework my launcher.


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Post by Wilson » Tue Sep 18, 2007 4:06 pm

Drag_Racer408a wrote:I think PVC should be allowed to be used for launchers ect. I know some people use steel and copper but for some the PVC is just easier and more reliable.

If the pvc is a saftey issue rather than an improper usage thing then the length between a presurized launcher or watever maybe should be increased.

I think some would get really mad about PVC beign banned because it is really cheap. As long as you stay within the saftey requirements of the rated pressure than it is really safe. I have only had a launcher 'blow up" once. But it wasn't really a pressre issue. It was a design flaw.

If PVC was indead banned then i personally would get pretty mad and probably drop the group. PVC is VERY safe if used properly. I know most of us around here are all pushing the limits to everything but the stuff is pretty safe.

Also your rocket would most likley blow up before your PVC launcher would because the sizes most used by our wrocket community can hold 600 PSI or more depending on the size.

Please no changes. I would not like this type of thing. I want stability in competition, not the "rule du jour".



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Post by Drag_Racer408a » Tue Sep 18, 2007 5:12 pm

I am glad to see i am not the only one out here liking PVC.

It is just so much easier to work with and make launchers with. With metal you have to own or buy a special threading tool so you can make hreads on it. It is also a lot cheaper than metal or any other thing. I can build a launcher totally out of PVC parts and still make it cheaper than buying a metal drainpipe launch tube.

The launcher that i use for A-1000FR costs under 7 dollars to buy all the parts for. Thats dirt cheap if you ask me.


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Post by WRA2 » Tue Sep 18, 2007 8:03 pm

Hello Everyone

We're not planning on changing the rules. We only put up the topic as an experiment.
We expected that there would be some disagreement among the competitors and it would turn into yet another heated debate. We never expected it to turn ugly so rapidly.

It just goes to show that we can't just go and arbitrarily change the rules because some people don't want to play by the same rules as everyone else.

We intend to leave the rules as they are unless someone tries to skirt the rules or violate the spirit of the rules with a loophole. We reserve the right to close loopholes or make clarifications to the wording to help make the content of the rules more precise.


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Post by WRA2 » Tue Sep 18, 2007 8:10 pm

tsumrall wrote: This is a good example of why your classes should be based on energy just like pyro-rocketry. If this was true then you could exclude PVC from high pressure systems but leave it in when it's safe to do so.
The weight limits for each class limit the amount of stored energy by limiting the size of the rocket.


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Re: PVC Used for parts under pressure

Post by WRA2 » Tue Sep 18, 2007 8:17 pm

Spaceman Spiff wrote:You already have the rules that require people stay 50 feet or more away and behind a shield and that should cover any PVC parts.
You are right Spaceman,

Perhaps more emphasis should be placed on the "50 feet from a pressurized rocket" rule or maybe a safety warning about PVC could be added.


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Post by U.S. Water Rockets » Wed Sep 19, 2007 8:53 am

You should have a "Don't Care" choice in this poll. We don't have any PVC in our system because it simply doesn't hold the pressures we need. Anybody who's comepting in Class "A" is not going to be using PVC parts.

In a category like your Class "C" then it's not an issue because the pressure vessel is going to fail long before the PVC pipes will shatter.



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Post by Cloud Dancers » Wed Sep 19, 2007 6:49 pm

Keep the PVC but use at your own risk. If you are following all the safety rules the dangers exploding PVC are a non issue (except maybe for your rocket BOOM!!!!)

There should be more stress on the 50 foot rule. Look what happened to this guy on the MSN group.

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His rocket exploded next to his face while he was pressing buttons on his camera on a fully pressurized rocket....Crazy!



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Post by 1KorBust » Sat Sep 29, 2007 7:14 pm

That's George Kats. He's very popular and has made lots of contributions to the water rocket group. It sets a bad example for kids if he doesn't follow the safety rules. I wish he had not made light of the accident.


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Post by WRA2 Admin » Mon Oct 08, 2007 6:19 pm

Keep the votes coming. Only about 10 days left until the poll closes.


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Post by rockets42 » Mon Oct 08, 2007 7:15 pm

1KorBust wrote:That's George Kats. He's very popular and has made lots of contributions to the water rocket group. It sets a bad example for kids if he doesn't follow the safety rules. I wish he had not made light of the accident.
Agreed, I think he said that after that incident he was reviewing their safety procedures. I am not sure he made light of the accident, but I think it highlights the fact that accidents happen and no matter how careful you are you always need to be vigelant. Look at what happened at Scaled composites and they pride themselves on safety.



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